It is known that polyurethane prepolymers are readily cured with metal salt complexes of methylenedianiline. See, for example, U.S. Pat. Nos. 3,755,261, 3,876,604 and 4,029,730.
For commercial purposes, the polyurethane prepolymer and metal salt complex of methylenedianiline are typically stored as a stable mixture, i.e., a one-component system, which is curable upon heating to an appropriate cure temperature. The one-component storage-stable system must necessarily not cure to an elastomeric or plastic state during storage, i.e., it must remain flowable. Several such one-component storage-stable polyurethane systems are known and are described in, for example, U.S. Pat. Nos. 5,102,969, 4,247,676, 4,950,715, 4,330,454, 5,064,494 and 4,778,845. These one-component polyurethane systems typically include a diisocyanate end-capped polypropylene oxide polyol having 3-15% free isocyanate monomer with 0.75-1.05 equivalents of methylenedianiline-NaCl complex.
Current one-component polyurethane systems are known to be storage-stable up to 30° C. See, for example, U.S. Pat. No. 4,778,845 to Tschan et al. However, there is a need in the art for one-component polyurethane systems having storage-stability at higher temperatures. It would be particularly advantageous for a one-component polyurethane system to maintain storage-stability for at least ninety days, and more preferably a year, at about 35° C., and even more, to maintain storage-stability for at least about thirty days at a temperature greater than 35° C. and up to about 50° C., and more preferably, for at least about thirty days at a temperature greater than 50° C. and up to about 70° C.
Accordingly, there is a need for new one-component compositions which are curable to elastomeric or plastic polyurethane product at an appropriate curing temperature while being stable and flowable during storage at higher temperatures than currently known in the art.